The present specification relates to infrared detectors.
Infrared detectors are often used to measure temperature changes within an area such as a room being monitored. One typical type of infrared detector includes a pyroelectric sensor. When a surface temperature of the pyroelectric sensor's dielectric changes, the dielectric generates an electric charge. In particular, polarization of the material forming the dielectric surface changes in response to a change in temperature, which generates a voltage across the dielectric. When the surface temperature rises, the polarization strength in the dielectric reduces, which results in a release of charge by the dielectric. The generated charge gradually drifts away from the dielectric surface. Infrared radiation incident upon the dielectric of the pyroelectric sensor continues. When the surface temperature of the dielectric reaches equilibrium, i.e., a constant temperature, it stops releasing a charge, and no signal is output. Thus, the pyroelectric sensor is used to detect temperature changes in an area being monitored.
Once a person enters the area being monitored, a change in the temperature of the area occurs. The infrared detector can detect these temperature changes, e.g., based on the pyroelectric sensor. Thus, based on signals outputted by the infrared detector, it can be determined whether or not someone enters the area being monitored.
However, conventional infrared detectors can only identify temperature changes and cannot detect when there is a static infrared signal source in the area being monitored. For example, if an elderly person enters the area being monitored and falls down in the area, a conventional infrared detector can only determine if the temperature changes in the area being monitored. Thus, the detector can determine that someone enters or leaves the area being monitored, but cannot determine that a continuous and static infrared signal source exists in the area being monitored. Consequently, the conventional detector would fail to determine that someone fell down in the area being monitored and as a result the detector cannot generate an alarm in response.
In some typical scenarios that require nursing care and monitoring, web cameras are often used to monitor the area. The camera is used to capture video images of the area and transmits the video images, for example, to a nursing station.
However, cameras generally have high power consumption and are powered by city electricity, which restricts installation and applications of the web cameras. In addition, since the web cameras produce images of the area being monitored, protecting the privacy of persons in the area being monitored restricts their use as well. For example, the web cameras typically cannot be installed in washing rooms and bedrooms.